We analyse whether the size of the local labour market allows for better matching between job seekers and vacancies, which is thought to enhance productivity. This analysis is based on a large data set providing detailed micro-level information on new employment relationships in Germany. Our results suggest rather small matching benefits. Doubling employment density increases the productivity of new employment relationships by 1.1% to 1.2%. Moreover, the findings indicate that the benefits accrue only to persons experiencing job-to-job transitions and short-term unemployed. We detect no important impact of agglomeration on transitions from long-term non-employed.